Mems microphone having diaphragm

ABSTRACT

AMEMS microphone includes a backplate that has a plurality of open areas, and a diaphragm spaced apart from the backplate. The diaphragm is deformable by sound waves to cause gaps between the backplate and the diaphragm being changed at multiple locations on the diaphragm. The diaphragm includes a plurality of anchor areas, located near a boundary of the diaphragm, which is fixed relative to the backplate. The diaphragm also includes multiple vent valves. Examples of the vent valve include a wing vent valve and a vortex vent valve.

REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. application Ser. No.16/016,996, filed on Jun. 25, 2018, the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND

A MEMS microphone generally includes a capacitive element formed with abackplate and a diaphragm spaced apart from the backplate. With the MEMSmicrophone, sound waves can be converted to electrical signals bysensing the capacitance of the capacitive element when the diaphragm isdeformed by energy of the sound waves.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A is a top view of a diaphragm in a MEMS microphone.

FIG. 1B is a cross-sectional views showing a MEMS microphone that isfabricated on a substrate.

FIG. 2A is a top view of a diaphragm having wing vent valves for usingin a MEMS microphone in accordance with some embodiments.

FIG. 2B is a cross-sectional view showing a MEMS microphone having adiaphragm with wing vent valves in accordance with some embodiments.

FIG. 2C is a top view of one of the sectors having a wing vent valve inaccordance with some embodiments.

FIG. 3 is a schematic showing the deflection of the diaphragm atmultiple locations with improved sensitivity for the MEMS microphone inaccordance with some embodiments.

FIG. 4A is a top view of a diaphragm having vortex vent valves for usingin a MEMS microphone in accordance with some embodiments.

FIG. 4B is a cross-sectional views showing a MEMS microphone having adiaphragm with vortex vent valves in accordance with some embodiments.

FIGS. 5A-5B are schematic drawings illustrating different possiblestructures of a curve trench on the diaphragm in accordance with someembodiments.

FIGS. 6A-6B are schematic drawings illustrating different possiblealignments between the vent valves on the diaphragm and the backplate inaccordance with some embodiments.

FIGS. 7A-7B are schematic drawings illustrating the deflection of thevortex vent valve under different test conditions in accordance withsome embodiments.

FIGS. 8A-81 are cross-sectional views showing a method of manufacturinga MEMS microphone that has a diaphragm with vent valves in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Many micro-electromechanical system (MEMS) device scan be manufacturedusing semiconductor device fabrication methods. Examples of these MEMSdevices include MEMS microphones, such as, a MEMS microphone 90 asillustrated in FIGS. 1A-1B. FIG. 1B is a cross-sectional view showing aMEMS microphone 90 that is fabricated on a substrate 40. The MEMSmicrophone 90 includes a backplate 60 and a diaphragm 50 spaced apartfrom the backplate 60. Both the backplate 60 and the diaphragm 50 can beelectrically conductive, which form a capacitive element. An electricalcontact 82 electrically connected to the backplate 60 forms a firstterminal for the capacitive element, and an electrical contact 84electrically connected to the diaphragm 50 forms a second terminal forthe capacitive element.

FIG. 1A is a top view of the diaphragm 50 of the MEMS microphone 90 inFIG. 1B. The cross section A-A′ of the diaphragm 50 is illustrated inFIG. 1B. The diaphragm 50 includes multiple venting holes 55 distributedon the diaphragm 50 (e.g., venting holes as shown or more). Thediaphragm 50 also includes one or more anchor areas 58 located near aboundary of the diaphragm 50. The anchor areas 58 allow the boundary ofthe diaphragm 50 to be fixed relative to the backplate 60 and allow gapsbetween the diaphragm and the backplate to be changed at the center ofthe diaphragm 50 and at other locations on the diaphragm at somedistance away from the anchor areas 58. The diaphragm 50 is deformableby energy of sound waves to make the diaphragm 50 bend towards or awayfrom the backplate 60, as the sound waves exert pressures on thediaphragm 50 through an opening 45 in the substrate 40. The backplate 60has multiple open areas 65. There is an air volume space 75 between thediaphragm 50 and the backplate 60. Air can get out of or get into theair volume space 75 through the air passages formed by the open areas 65on the backplate 60 and/or by the venting holes 55 on the the diaphragm50, as the diaphragm 50 bends towards or away from the backplate 60.

The bending movement of the diaphragm 50 relative to the backplate 60caused by the sound waves changes the capacitance of the capacitiveelement between the diaphragm 50 and the backplate 60. Such change ofthe capacitance can be measured with the electrical contact 82 and theelectrical contact 84. For the same amount of air pressure exerted onthe diaphragm 50 by the sound waves, if the rigidity of the diaphragm 50decreases, the amount of the bend of the diaphragm 50 caused by thesound waves increases and the induced change of the capacitanceincreases as well. That is, decreasing the rigidity of the diaphragm 50improves the sensitivity of the MEMS microphone 90. The rigidity of thediaphragm 50 can be decreased by selecting the material for making thediaphragm or by decreasing the thickness (“t” as shown in FIG. 1B) ofthe diaphragm.

The diaphragm 50 in the MEMS microphone 90 generally has to withstand anair blow test. For example, when the air pressure exerted on thediaphragm 50 by the air blow test is at about 0.2 MPa, the chance ofgetting the diaphragm 50 broken should be statistically negligible underaccepted statistical standard. While increasing the rigidity of thediaphragm 50 can decrease the chance of breaking the diaphragm 50, suchincreasing of the rigidity also lowers the sensitivity of the MEMSmicrophone 90. In an alternative method, increasing the size of theventing holes 55 and/or increasing the total number of the venting holes55 to increase overall open ratio can also decrease the chance ofbreaking the diaphragm 50. But such measure of increasing open ratioalso lowers the sensitivity of the MEMS microphone 90, because suchmeasure also lowers the sensing area. Furthermore, increasing open ratiomay also increase the low corner frequency of the MEMS microphone 90,making it less sensitive to low frequency sound waves. It is desirableto have an improved structure of the diaphragm that has improved chanceof surviving air blow tests without losing the sensitivity of the MEMSmicrophone.

FIGS. 2A-2C illustrate the structure of a diaphragm having wing ventvalves for using in a MEMS microphone in accordance with someembodiments. As shown in FIG. 2B, a MEMS microphone 90 includes abackplate 60 and a diaphragm 100 constructed on a substrate 40. Thebackplate 60 has multiple open areas 65. The diaphragm 100 is spacedapart from the backplate 60 and deformable by energy of sound waves tocause gaps between the backplate 60 and the diaphragm 100 being changedat multiple locations on the diaphragm. For example, the diaphragm 100can be bent away or bent towards the backplate 60. In many situations,when the diaphragm 100 is bent, the gap change between the backplate 60and the diaphragm 100 at a first location near the center of thediaphragm 100 is often large than the gap change between the backplate60 and the diaphragm 100 at a second location near the boundary of thediaphragm 100, if the above mentioned first location and second locationare located on a same radius line on the diaphragm 100. In theembodiments as shown in FIGS. 2A-2C, there are also multiple anchorareas 120 located near the boundary of the diaphragm 100. The parts ofthe diaphragm in the anchor areas 120 are fixed relative to thebackplate 60. That is, the gap between the backplate 60 and thediaphragm 100 at locations in the anchor areas 120 does not change whenthe diaphragm 100 is bent by sound waves.

In the embodiments as shown in FIGS. 2A-2C, the diaphragm 100 includesmultiple sectors 110. As shown in FIG. 2C, the sector 110 is withinthree boundary segments: an arc 113 and two boundary radius 111 and 112.On the diaphragm 100, the arc 113 is positioned between neighboringanchor areas 120 and within a boundary 115 of the diaphragm 100. Thesector 110 includes a wing vent valve 130. The wing vent valve 130includes a first vent slot 136 extending along a first radius 117, asecond vent slot 138 extending along a second radius 119, and a thirdvent slot 135 joining the first vent slot 136 and the second vent slot138. Each of the three vent slots 136, 138, and 135 on the diaphragm 100is a slot opening that allows air to pass through. In some embodiments,the third vent slot 135 is located in an area close to the arc 113 nearthe boundary of the diaphragm 100. In some embodiments, the third ventslot 135 can be located in an area that is at some distance from the arc113.

In some embodiments, the third vent slot 135 can join an end of thefirst vent slot 136 with an end of the second vent slot 138, as shown inFIG. 2C. In some embodiments, the third vent slot 135 can join the firstvent slot 136 with the second vent slot 138 at locations other than theends of the two vent slots 136 and 138. In some embodiments, the thirdvent slot 135 can extend along an arc 115 within the sector 110, asshown in FIG. 2C. In some embodiments, the third vent slot 135 can jointhe first vent slot 136 and the second vent slot 138 with a straightline.

As shown in FIGS. 2B-2C, the sector 110 has a radius length R_(l). Insome embodiments, wherein the first vent slot 136 and the second ventslot 138 each have a length that is a fraction of a radius length of thesector 110. In some embodiments, the first vent slot 136 and second ventslot 138 each have a length that is less than one fourth of the radiuslength R_(l) of the sector 110. As shown in FIG. 2C, the sector 110 hasan angular span θ″, and the third vent slot 135 has an angular span θ.In some embodiments, the clamped ratio of the sector 110, (θ″−θ)/θ″, iswithin a range of 10% to 70%. The clamped ratio of the diaphragm 100 cantake the form of (2π−Σθ_(i))/2π, where Σθ_(i) is the sum of angularspans of the third vent slot in all sectors of the diaphragm 100. Insome embodiments, the clamped ratio of the diaphragm 100 is within arange of 10% to 70%. In some embodiments, when all sectors of thediaphragm 100 are substantially identical, the clamped ratio of thediaphragm 100 is substantially the same as the clamped ratio of eachsector.

FIG. 3 illustrates a schematic showing the deflection of the diaphragm100 at multiple locations with improved sensitivity for the MEMSmicrophone in accordance with some embodiments. In FIG. 3, thedeflection of the diaphragm 100 at membrane locations along tworepresentative radii OA and OB are shown as a function of membranelength ranging from the origin to the edge of the diaphragm 100. Theradius OA extends in a direction that bypasses the wing vent valve 130.The radius OB extends in a direction that passes through the wing ventvalve 130. The deflection of the diaphragm 100 at the end of the radiusOA is fixed and does not depend upon the pressure exerts on thediaphragm 100, because the end of the radius OA is anchored in one ofthe anchor areas.

The difference between the deflection of the diaphragm 100 at the originand the deflection of the diaphragm 100 at the end of the radius OAcharacterizes the largest gap change between the backplate 60 and thediaphragm 100, which happens at the center location of the diaphragm100. The gap change between the backplate 60 and the diaphragm 100 at alocation along the radius OA decreases as such location moves away fromthe origin and towards the end of the radius OA. The gap change betweenthe backplate 60 and the diaphragm 100 at a location along the radius OBalso decreases as such location moves from the origin towards the end ofthe radius OB. The gap change at a location along the radius OB near theedge areas, however, is significantly larger than the gap change at alocation along the radius OA near the edge areas, because of theimplementation of the wing vent valve 130 on the diaphragm 100. Suchlarger gap change at locations near the edge areas within the angularspan θ of the third vent slot 135 (as shown in FIG. 2C) results inlarger capacitive change of the capacitive element formed between thebackplate 60 and the diaphragm 100. Consequently, the implementation ofthe wing vent valve 130 on the diaphragm 100 results in increasedsensitivity of the MEMS microphone 90.

Implementing the wing vent valve 130 on the diaphragm 100 not only canincrease microphone sensitivity but also can make the diaphragm 100 topass some common air blow test more easily. In some embodiments, it ispossible to select some designs of the diaphragm 100 to make the wingvent valve deflection to stay within a predetermined range. For example,with some designs of the diaphragm 100, deflection of the wing ventvalve can be made smaller than 0.1 μm while the air blow pressure ismuch smaller than 0.2 MPa, and it can be made larger than 0.5 μm whilethe air blow pressure is much larger than 0.2 MPa. In most of the abovemotioned selected designs, the first vent slot 136 and second vent slot138 each have a length that is less than one fourth of a radius lengthof the sector 110, and the clamped ratio of the sector is within a rangeof 10% to 70%. Some these selected designs can enhance microphonesensitivity while causing slight rigidity degradation in the diaphragm100. Additionally, in some embodiments, rigidity degradation in thediaphragm 100 can be compensated by some techniques with some enhancedrigidity in the diaphragm 100. For example, when the diaphragm 100 issubject to an anneal process, it is possible to enhance the rigidity inthe diaphragm 100 by increasing 0.1 Mpa to 20 MPa membrane stressinduced from the anneal process.

In addition to the diaphragm 100 having the wing vent valve 130, thereare other embodiments of the diaphragm 100 that can increase microphonesensitivity and pass some common air blow test. FIGS. 4A-4B illustratethe structure of a diaphragm 100 having vortex vent valve 140 for usingin a MEMS microphone in accordance with some embodiments. FIG. 4B is across-sectional views showing a MEMS microphone 90 having a diaphragm100 with vortex vent valves 140 in accordance with some embodiments. Asshown in FIG. 4B, a MEMS microphone 90 includes a backplate 60 and adiaphragm 100 constructed on a substrate 40. The backplate 60 hasmultiple open areas 65. The diaphragm 100 is spaced apart from thebackplate 60 and deformable by energy of sound waves to cause gapsbetween the backplate 60 and the diaphragm 100 being changed at multiplelocations on the diaphragm. In the embodiments as shown in FIGS. 4A-4B,there are one or more anchor areas 120 located near the boundary of thediaphragm 100 such that the boundary of the diaphragm 100 is fixedrelative to the backplate 60. That is, the gap between the backplate 60and the diaphragm 100 the boundary of the diaphragm 100 does not changewhen the diaphragm 100 is bent by sound waves.

FIG. 4A is a top view of a diaphragm 100 having vortex vent valves 140for using in a MEMS microphone 90 in accordance with some embodiments.In FIG. 4A, as illustrated, the shape of each vortex vent valve 140 onthe diaphragm 100 is in the form of a curve trench. Each curve trenchextending from a first location 142 near a center of the diaphragm to asecond location 144 near the boundary of the diaphragm. Mathematically,a curve trench can be represented as r(θ), that is, the radius r of alocation on the curve trench is a function of its polar angle θ. In theembodiments as shown in FIG. 4A, a first linear distance between twocurve trenches at the first location 142 near the center of thediaphragm is smaller than a second linear distance between the two curvetrenches at the second location 144 near the boundary of the diaphragm.For example, as shown in FIG. 4A, the linear distance CD is smaller thanthe linear distance AB. If the first location near the center of thediaphragm for the two curve trenches is respectively (r_(C), θ_(C)) and(r_(D), θ_(D)), and if the second location near the boundary of thediaphragm for the two curve trenches is respectively (r_(A), θ_(A)) and(r_(B), θ_(B)), then,

$\sqrt{\left( {{r_{C}\cos \; \theta_{C}} - {r_{D}\cos \; \theta_{D}}} \right)^{2} + \left( {{r_{C}\sin \; \theta_{C}} - {r_{D}\sin \; \theta_{D}}} \right)^{2}} < {\sqrt{\left( {{r_{A}\cos \; \theta_{A}} - {r_{B}\cos \; \theta_{B}}} \right)^{2} + \left( {{r_{A}\sin \; \theta_{A}} - {r_{B}\sin \; \theta_{B}}} \right)^{2}}.}$

Here, r_(A) and r_(B) are respectively the radius distance of the firstlocation near the center of the diaphragm for the two curve trenches asshown in FIG. 4A, while r_(C) and r_(D) are respectively the radiusdistance of the second location near the boundary of the diaphragm forthe two curve trenches as shown in FIG. 4A. In some embodiments, each ofthe curve trenches on the diaphragm 100 is identical in shape, and forthe two curve trenches as identified in the figure, r_(C)=r_(D) andr_(A)=r_(B). In some embodiments, however, some of the curve trenches onthe diaphragm 100 can have different shapes.

FIGS. 5A-5B are schematic drawings illustrating different possiblestructures of a curve trench on the diaphragm in accordance with someembodiments. In some embodiments, as shown in FIG. 5A, a curve trench140 can have a width that changes with its location on the curve trench.In some embodiments, as shown in FIG. 5B, a curve trench 140 can have auniform width.

FIGS. 6A-6B are schematic drawings illustrating different possiblealignments between the vent valves on the diaphragm 100 and thebackplate 60 in accordance with some embodiments. In some embodiments,as shown in FIG. 6A, a vent valve can be placed behind a non-open areain the backplate 60. In FIG. 6A, the air flow passing through the ventvalve is blocked by the non-open area in the backplate 60. In someembodiments, as shown in FIG. 6B, a vent valve can be placed behind anopen area in the backplate 60. In FIG. 6B, the air flow passing throughthe vent valve can directly pass through the open area in the backplate60.

The diaphragm 100 having vortex vent valves can also be designed to passsome common air blow test. FIGS. 7A-7B are schematic drawingsillustrating the deflection of the vortex vent valve under differenttest conditions in accordance with some embodiments. The lower figure inFIG. 7A is a top view of the diaphragm 100 while the lower figure inFIG. 7A is a side view of the diaphragm 100. In some embodiments, asshown in the lower figure in FIG. 7A, when the air blow pressure is muchsmaller than 0.2 MPa, the vortex vent valve 140 essentially does notmove much (as indicated by the dashed line near the vent value), anddeflection of the vortex vent valve 140 can be made smaller than 0.1 μm.In some embodiments, as shown in FIG. 7B, when the air blow pressure ismuch larger than 0.2 MPa, deflection of the vortex vent valve 140 can bemade larger than 0.5 μm. Additionally, as shown in FIG. 7B, one side ofthe the vortex vent valve 140 can have an up deflection while the otherside of the the vortex vent valve 140 can have a down deflection.

FIGS. 8A-81 are cross-sectional views showing a method of manufacturinga MEMS microphone 90 that has a diaphragm 100 with vent valves inaccordance with some embodiments.

As shown in a cross-sectional view in FIG. 8A, a substrate 40 isprovided. In various embodiments, the substrate 40 can be, for example,silicon, glass, silicon dioxide, aluminum oxide, or the like. A firstoxide layer 70A is formed on the substrate 40. The first oxide layer 70Acan be an oxide material (e.g., SiO2). The first oxide layer 70A can beformed by way of a thermal process. In other embodiments, the firstoxide layer 70A can be formed by a deposition process, such as, chemicalvapor deposition (CVD), physical vapor deposition (PVD), or atomic layerdeposition (ALD).

After forming the first oxide layer 70A, the first oxide layer 70A isetched according to a first masking layer (not shown) to form aplurality of via holes, such as, a via hole 86A as shown in FIG. 8A. Insome embodiments, the first masking layer can include photoresist or anitride (e.g., Si₃N₄) patterned using a photolithography process. Insome embodiments, the etchant can include a dry etchant have an etchingchemistry comprising a fluorine species (e.g., CF₄, CHF₃, C₄F₈, etc.).In some embodiments, the etchant can include a wet etchant, such as,hydrofluoric acid (HF), Buffered Oxide Etch (BOE) solution (6 parts 40%NH₄F and 1 part 49% HF), or Tetramethylammonium hydroxide (TMAH).

In the next step, as shown in FIG. 8B, a layer of poly-silicon isdeposited on top of the first oxide layer 70A with a suitable technique,such as chemical vapor deposition (CVD). After the deposition process,this layer of poly-silicon is subject to a polish process, such aschemical mechanical polishing (CMP) process, for planarization. Then,this layer of poly-silicon is etched according to a second masking layer(not shown) to form a diaphragm 100 including multiple vent valves. Insome embodiments, at least one of the vent valves includes a part thatis configured to deflect under air pressure when the air pressure islarger than a predetermined value. In some embodiments, the diaphragm100 formed during the etching process can have multiple wing ventvalves, such as, the wing vent valve 130 as shown in FIG. 2A. In someembodiments, the diaphragm 100 formed during the etching process canhave multiple vortex vent valves, such as, the vortex vent valve 140 asshown in FIG. 4A.

In the next step, as shown in FIG. 8C, a second oxide layer 70B isdeposited on top of the diaphragm 100 with a suitable technique, such aschemical vapor deposition (CVD). Many of the techniques for depositingthe first oxide layer 70A as described previously can also be used fordepositing the second oxide layer 70B. After the deposition process,this second oxide layer 70B is subject to a polish process, such aschemical mechanical polishing (CMP) process, for planarization. Then,this second oxide layer 70B is etched according to a third masking layer(not shown) to form via holes (e.g., via holes 84B, 86B, and 88B).

In the next step, as shown in FIG. 8D, a backplate layer is deposited ontop of the second oxide layer 70B with a suitable technique. In someembodiments, the backplate layer is formed by depositing a layer ofpoly-silicon with a suitable technique, such as chemical vapordeposition (CVD). In some embodiments, the backplate layer includesthree layers which are formed by first depositing a layer of siliconnitride, continued by depositing a layer of poly-silicon, and followedby depositing another layer of silicon nitride. Each of these threelayers can be formed with chemical vapor deposition (CVD), or any othersuitable techniques. After the deposition of the backplate layer, thisbackplate layer is subject to a polish process, such as chemicalmechanical polishing (CMP) process, for planarization. Then, thisbackplate layer is etched according to a fourth masking layer (notshown) to form a backplate 60 including multiple open areas 65.

In the next step, as shown in FIG. 8E, a third oxide layer 70C isdeposited on top of the backplate layer including the backplate 60. Manyof the techniques for depositing the first oxide layer 70A as describedpreviously can also be used for depositing the third oxide layer 70C.After the deposition process, this third oxide layer 70C is subject to apolish process, such as chemical mechanical polishing (CMP) process, forplanarization. Then, this third oxide layer 70C is etched according to afifth masking layer (not shown) to form via holes (e.g., via holes 82C,84C, 86C, and 88C).

In the next step, as shown in FIG. 8F, a metal contact layer isdeposited on top of the third oxide layer 70C. This metal contact layeris etched according to a sixth masking layer (not shown) to form metalcontacts (e.g., metal contacts 82, 84, 86, and 88). Examples of thematerials for forming the metal contacts include silver, gold, copper,aluminum, aluminum-copper alloy, gold-copper alloy or other suitableconductive materials. In FIG. 8F, the first oxide layer 70A, the secondoxide layer 70B, and the third oxide layer 70C collectively form anoxide layer 70 that provide electrical isolation and mechanical supportsfor various components on the substrate 40.

In the next step, as shown in FIG. 8G, a first protection layer 72 isdeposited on the oxide layer 70 and on the metal contacts, and a secondprotection layer 42 is deposited on the substrate 40. Example protectionlayers for the first protection layer 72 and the second protection layer42 include a photoresists layer or a dielectric material layer (e.g.,silicon nitride). Some areas of the second protection layer 42 areremoved to form a protection mask on the substrate 40 that opens upselected parts of the substrate 40 for an etching process. Next, thesubstrate 40 is etched according to the protection mask formed by thesecond protection layer 42 to create an opening 45 on the substrate 40.In some embodiments, the opening 45 on the substrate 40 can be opened upby anisotropic plasma etching.

In the next step, as shown in FIG. 8H, some areas of the firstprotection layer 72 are removed to form a protection mask on the oxidelayer 70 and on the metal contacts. This protection mask formed by thefirst protection layer 72 opens up an opening 75 exposing the oxidelayer 70 for an etching process. Next, the oxide layer 70 is etched witha wet etchant, starting from both the opening 45 on the substrate 40 andthe opening 75 on the oxide layer 70, to form the suspended diaphragm100 and the suspended backplate 60. Examples of the wet etchant that canbe used for etching the oxide layer 70 include hydrofluoric acid (HF),Buffered Oxide Etch (BOE) solution (6 parts 40% NH₄F and 1 part 49% HF),or Tetramethylammonium hydroxide (TMAH)).

In the next step, as shown in FIG. 8I, both the first protection layer72 and the second protection layer 42 are removed. These protectionlayers can be stripped off with chemicals or etched away with etchant.After removing these protection layers, the MEMS microphone 90 havingthe diaphragm 100 with vent valves is fabricated.

In FIG. 8I, the MEMS microphone 90 as fabricated includes an electricalcontact 82 electrically connected to the backplate 60 that forms a firstterminal for the capacitive element, and an electrical contact 84electrically connected to the diaphragm 50 that forms a second terminalfor the capacitive element. In addition, the MEMS microphone 90 caninclude one or more contacts (e.g., a contact 86, the only one shown inthe figure) that connect to pre-fabricated CMOS circuits (not shown inthe figure) on the substrate through via holes. The pre-fabricated CMOScircuits can provide the electronics for supporting the operation of theMEMS microphone 90. In some embodiments, the pre-fabricated CMOScircuits can be fabricated, using suitable process, on the substrate 40before the first oxide layer 70A is formed on the substrate 40 (as shownin FIG. 8A). Furthermore, the MEMS microphone 90 can include a contact88, passing through a via hole, that connects to an electronic componentin the conducting layer for constructing the diaphragm 100, to providean electronic grounding if needed.

Some aspects of the present disclosure relate to a microphone. Themicrophone includes a backplate that has a plurality of open areas, anda diaphragm spaced apart from the backplate. The diaphragm is deformableby sound waves to cause gaps between the backplate and the diaphragmbeing changed at multiple locations on the diaphragm. The diaphragmincludes a plurality of anchor areas, located near a boundary of thediaphragm, which is fixed relative to the backplate. The diaphragm alsoincludes a sector with its arc located between neighboring anchor areas.The sector includes a wing vent valve. The wing vent valve includes afirst vent slot extending along a first radius, a second vent slotextending along a second radius, and a third vent slot joining the firstvent slot and the second vent slot.

Other aspects of the present disclosure relate to a microphone. Themicrophone includes a backplate that has a plurality of open areas, anda diaphragm spaced apart from the backplate. The diaphragm is deformableby sound waves to cause gaps between the backplate and the diaphragmbeing changed at multiple locations on the diaphragm. The diaphragmincludes one or more anchor areas, located near a boundary of thediaphragm, which is fixed relative to the backplate. The diaphragmincludes a plurality of curve trenches. Each curve trench extending froma first location near a center of the diaphragm to a second locationnear the boundary of the diaphragm. A first linear distance between twocurve trenches at the first location near the center of the diaphragm issmaller than a second linear distance between the two curve trenches atthe second location near the boundary of the diaphragm.

Still other aspects of the present disclosure relate to a method ofmanufacturing a microphone. A first layer of conducting material isformed on a first layer of insulating material supported by a substrate.A first pattern in a diaphragm is formed in the first layer ofconducting material, and this pattern includes multiple vent valves. Asecond layer of conducting material is formed on a second layer ofinsulating material supported by the first layer of conducting material.A second pattern in a backplate is formed in the second layer ofconducting material, and this pattern includes multiple open areas. Thesubstrate is etched according to a first protection mask formed on thesubstrate to create a first opening in the substrate. A second openingis created in a second protection mask formed on a third layer ofinsulating material supported by the second layer of conductingmaterial. The first layer of insulating material, the second layer ofinsulating material, and the third layer of insulating material areetched to create a capacitive structure that includes parts of thediaphragm and the backplate being suspended in air.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method of manufacturing a microphone, themethod comprising: forming a first layer of conducting material on afirst layer of insulating material supported by a substrate; forming afirst pattern in a diaphragm, in the first layer of conducting material,that includes multiple vent valves; forming a second layer of conductingmaterial on a second layer of insulating material supported by the firstlayer of conducting material; forming a second pattern in a backplate,in the second layer of conducting material, that includes multiple openareas; etching the substrate according to a first protection mask formedon the substrate to create a first opening in the substrate; creating asecond opening in another protection mask formed on a third layer ofinsulating material supported by the second layer of conductingmaterial; and etching the first layer of insulating material, the secondlayer of insulating material, and the third layer of insulatingmaterial, to create a capacitive structure that includes parts of thediaphragm and the backplate being suspended in air.
 2. The method ofclaim 1, wherein at least one of the vent valves is a wing vent valve.3. The method of claim 1, wherein at least one of the vent valves is avortex vent valve.
 4. The method of claim 1, wherein at least one of thevent valves includes a part that is configured to deflect under airpressure when the air pressure is larger than a predetermined value. 5.The method of claim 1, wherein a wing vent valve structure includes acurve trench extending from a first location near a center of thediaphragm to a second location near an outer edge of the diaphragm, andwherein the curve trench has a width thereof changing from the firstlocation to the second location.
 6. The method of claim 1, wherein atleast one of the vent valves includes a first vent slot extending alonga first radius of the diaphragm, a second vent slot extending along asecond radius of the diaphragm, and a third vent slot joining the firstvent slot and the second vent slot, wherein the first vent slot and thesecond vent slot each have a length that is less than one fourth of aradius length of the diaphragm from a center of the diaphragm to anouter edge of the diaphragm.
 7. The method of claim 1: wherein at leastone of the vent valves includes a plurality of curve trenches, a curvetrench extending from a first location near a center of the diaphragm toa second location near a boundary of the diaphragm, and wherein thecurve trench has a width thereof changing with its location at the curvetrench.
 8. The method of claim 1, wherein the diaphragm comprisespoly-silicon material and wherein the backplate comprises poly-siliconmaterial.
 9. A method, comprising: forming a first layer of insulatingmaterial over a substrate; forming a first layer of conducting materialover the first layer of insulating material, and patterning multiplevent valve structures in the first layer of conducting material; forminga second layer of insulating material over the first layer of conductingmaterial and over the multiple vent valve structures; forming a secondlayer of conducting material over the second layer of insulatingmaterial, and forming multiple open areas in the second layer ofconducting material; forming a third layer of insulating material overthe second layer of conducting material; and forming an opening in thesubstrate to expose a lower surface of the first layer of insulatingmaterial; concurrently etching the first layer of insulating material,the second layer of insulating material, and the third layer ofinsulating material, to suspend a diaphragm portion of the first layerof conducting material and a backplate portion of the second layer ofconducting material in air.
 10. The method of claim 9, whereinconcurrently etching the first layer of insulating material, the secondlayer of insulating material, and the third layer of insulating materialincludes an etch comprising: hydrofluoric acid (HF), Buffered Oxide Etch(BOE) solution (6 parts 40% NH₄F and 1 part 49% HF), orTetramethylammonium hydroxide (TMAH).
 11. The method of claim 9, whereinthe diaphragm portion comprises poly-silicon material.
 12. The method ofclaim 9, wherein the backplate portion comprises a layer of poly-siliconmaterial.
 13. The method of claim 9, wherein at least one of themultiple vent valve structures includes a curve trench extending from afirst location near a center of the diaphragm portion to a secondlocation near an outer edge of the diaphragm portion, and wherein thecurve trench has a width thereof changing from the first location to thesecond location.
 14. The method of claim 9, wherein at least one of themultiple vent valve structures includes a first vent slot extendingalong a first radius of the diaphragm portion, a second vent slotextending along a second radius of the diaphragm portion, and a thirdvent slot joining the first vent slot and the second vent slot, whereinthe first vent slot and the second vent slot each have a length that isless than one fourth of a radius length of the diaphragm portion from acenter of the diaphragm portion to an outer edge of the diaphragmportion.
 15. The method of claim 9: wherein at least one of the multiplevent valve structures includes a plurality of curve trenches, each curvetrench extending from a first location near a center of the diaphragmportion to a second location near a boundary of the diaphragm portion,and wherein at least one curve trench has a width thereof changing withits location at the at least one curve trench.
 16. The method of claim9, wherein prior to the concurrent etching of the first layer ofinsulating material, the second layer of insulating material, and thethird layer of insulating material, the multiple vent valve structuresare fixed; but after the concurrent etching of the first layer ofinsulating material, the second layer of insulating material, and thethird layer of insulating material, the multiple vent valve structureseach include a part that is configured to deflect under an air pressuredifference between an upper surface of the part and the lower surface ofthe part when the air pressure difference is larger than a predeterminedvalue.
 17. A method, comprising: forming a first layer of insulatingmaterial over a substrate; forming a first layer of conducting materialover the first layer of insulating material, and patterning the firstlayer of conducting material to establish a diaphragm structure thatincludes multiple wing vent valve structures; and wherein a wing ventvalve structure of the multiple wing vent valve structures includes acurve trench extending from a first location near a center of thediaphragm structure to a second location near an outer edge of thediaphragm structure, and wherein the curve trench has a width thereofchanging from the first location to the second location; or wherein awing vent valve structure of the multiple wing vent valve structuresincludes a first vent slot extending along a first radius of thediaphragm structure, a second vent slot extending along a second radiusof the diaphragm structure, and a third vent slot joining the first ventslot and the second vent slot, wherein the first vent slot and thesecond vent slot each have a length that is less than one fourth of aradius length of the diaphragm structure from the center of thediaphragm structure to the outer edge of the diaphragm structure. 18.The method of claim 17, wherein the diaphragm structure comprisespoly-silicon material.
 19. The method of claim 17, further comprising:forming a second layer of insulating material over the first layer ofconductive material; forming a second layer of conductive material overthe second layer of insulating material; and. forming a third layer ofinsulating material over the second layer of conductive material. 20.The method of claim 19, further comprising: performing in situ etchingof the first layer of insulating material, the second layer ofinsulating material, and the third layer of insulating material, tosuspend the diaphragm structure in air.